Use ASP.NET MVC validation with jquery ajax?

Client Side

Using the jQuery.validate library should be pretty simple to set up.

Specify the following settings in your Web.config file:

<appSettings>
    <add key="ClientValidationEnabled" value="true"/> 
    <add key="UnobtrusiveJavaScriptEnabled" value="true"/> 
</appSettings>

When you build up your view, you would define things like this:

@Html.LabelFor(Model => Model.EditPostViewModel.Title, true)
@Html.TextBoxFor(Model => Model.EditPostViewModel.Title, 
                                new { @class = "tb1", @Style = "width:400px;" })
@Html.ValidationMessageFor(Model => Model.EditPostViewModel.Title)

NOTE: These need to be defined within a form element

Then you would need to include the following libraries:

<script src='@Url.Content("~/Scripts/jquery.validate.js")' type='text/javascript'></script>
<script src='@Url.Content("~/Scripts/jquery.validate.unobtrusive.js")' type='text/javascript'></script>

This should be able to set you up for client side validation

Resources

http://msdn.microsoft.com/en-us/vs2010trainingcourse_aspnetmvccustomvalidation_topic5.aspx

Server Side

NOTE: This is only for additional server side validation on top of jQuery.validation library

Perhaps something like this could help:

[ValidateAjax]
public JsonResult Edit(EditPostViewModel data)
{
    //Save data
    return Json(new { Success = true } );
}

Where ValidateAjax is an attribute defined as:

public class ValidateAjaxAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        if (!filterContext.HttpContext.Request.IsAjaxRequest())
            return;

        var modelState = filterContext.Controller.ViewData.ModelState;
        if (!modelState.IsValid)
        {
            var errorModel = 
                    from x in modelState.Keys
                    where modelState[x].Errors.Count > 0
                    select new
                           {
                               key = x,
                               errors = modelState[x].Errors.
                                                      Select(y => y.ErrorMessage).
                                                      ToArray()
                           };
            filterContext.Result = new JsonResult()
                                       {
                                           Data = errorModel
                                       };
            filterContext.HttpContext.Response.StatusCode = 
                                                  (int) HttpStatusCode.BadRequest;
        }
    }
}

What this does is return a JSON object specifying all of your model errors.

Example response would be

[{
    "key":"Name",
    "errors":["The Name field is required."]
},
{
    "key":"Description",
    "errors":["The Description field is required."]
}]

This would be returned to your error handling callback of the $.ajax call

You can loop through the returned data to set the error messages as needed based on the Keys returned (I think something like $('input[name="' + err.key + '"]') would find your input element

---

What you should do is to serialize your form data and send it to the controller action. ASP.NET MVC will bind the form data to the EditPostViewModel object( your action method parameter), using MVC model binding feature.

You can validate your form at client side and if everything is fine, send the data to server. The valid() method will come in handy.

$(function () {

    $("#yourSubmitButtonID").click(function (e) {

        e.preventDefault();
        var _this = $(this);
        var _form = _this.closest("form");

        var isvalid = _form .valid();  // Tells whether the form is valid

        if (isvalid)
        {           
           $.post(_form.attr("action"), _form.serialize(), function (data) {
              //check the result and do whatever you want
           })
        }

    });

});

---

Here's a rather simple solution:

In the controller we return our errors like this:

if (!ModelState.IsValid)
        {
            return Json(new { success = false, errors = ModelState.Values.SelectMany(x => x.Errors).Select(x => x.ErrorMessage).ToList() }, JsonRequestBehavior.AllowGet);
        }

Here's some of the client script:

function displayValidationErrors(errors)
{
    var $ul = $('div.validation-summary-valid.text-danger > ul');

    $ul.empty();
    $.each(errors, function (idx, errorMessage) {
        $ul.append('<li>' + errorMessage + '</li>');
    });
}

That's how we handle it via ajax:

$.ajax({
    cache: false,
    async: true,
    type: "POST",
    url: form.attr('action'),
    data: form.serialize(),
    success: function (data) {
        var isSuccessful = (data['success']);

        if (isSuccessful) {
            $('#partial-container-steps').html(data['view']);
            initializePage();
        }
        else {
            var errors = data['errors'];

            displayValidationErrors(errors);
        }
    }
});

Also, I render partial views via ajax in the following way:

var view = this.RenderRazorViewToString(partialUrl, viewModel);
        return Json(new { success = true, view }, JsonRequestBehavior.AllowGet);

RenderRazorViewToString method:

public string RenderRazorViewToString(string viewName, object model)
    {
        ViewData.Model = model;
        using (var sw = new StringWriter())
        {
            var viewResult = ViewEngines.Engines.FindPartialView(ControllerContext,
                                                                     viewName);
            var viewContext = new ViewContext(ControllerContext, viewResult.View,
                                         ViewData, TempData, sw);
            viewResult.View.Render(viewContext, sw);
            viewResult.ViewEngine.ReleaseView(ControllerContext, viewResult.View);
            return sw.GetStringBuilder().ToString();
        }
    }

---

Added some more logic to solution provided by @Andrew Burgess. Here is the full solution:

Created a action filter to get errors for ajax request:

public class ValidateAjaxAttribute : ActionFilterAttribute
    {
        public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            if (!filterContext.HttpContext.Request.IsAjaxRequest())
                return;

            var modelState = filterContext.Controller.ViewData.ModelState;
            if (!modelState.IsValid)
            {
                var errorModel =
                        from x in modelState.Keys
                        where modelState[x].Errors.Count > 0
                        select new
                        {
                            key = x,
                            errors = modelState[x].Errors.
                                                          Select(y => y.ErrorMessage).
                                                          ToArray()
                        };
                filterContext.Result = new JsonResult()
                {
                    Data = errorModel
                };
                filterContext.HttpContext.Response.StatusCode =
                                                      (int)HttpStatusCode.BadRequest;
            }
        }
    }

Added the filter to my controller method as:

[HttpPost]
// this line is important
[ValidateAjax]
public ActionResult AddUpdateData(MyModel model)
{
    return Json(new { status = (result == 1 ? true : false), message = message }, JsonRequestBehavior.AllowGet);
}

Added a common script for jquery validation:

function onAjaxFormError(data) {
    var form = this;
    var errorResponse = data.responseJSON;
    $.each(errorResponse, function (index, value) {
        // Element highlight
        var element = $(form).find('#' + value.key);
        element = element[0];
        highLightError(element, 'input-validation-error');

        // Error message
        var validationMessageElement = $('span[data-valmsg-for="' + value.key + '"]');
        validationMessageElement.removeClass('field-validation-valid');
        validationMessageElement.addClass('field-validation-error');
        validationMessageElement.text(value.errors[0]);
    });
}

$.validator.setDefaults({
            ignore: [],
            highlight: highLightError,
            unhighlight: unhighlightError
        });

var highLightError = function(element, errorClass) {
    element = $(element);
    element.addClass(errorClass);
}

var unhighLightError = function(element, errorClass) {
    element = $(element);
    element.removeClass(errorClass);
}

Finally added the error javascript method to my Ajax Begin form:

@model My.Model.MyModel
@using (Ajax.BeginForm("AddUpdateData", "Home", new AjaxOptions { HttpMethod = "POST", OnFailure="onAjaxFormError" }))
{
}

---

You can do it this way:

(Edit: Considering that you're waiting for a response json with dataType: 'json')

.NET

public JsonResult Edit(EditPostViewModel data)
{
    if(ModelState.IsValid) 
    {
       // Save  
       return Json(new { Ok = true } );
    }

    return Json(new { Ok = false } );
}

JS:

success: function (data) {
    if (data.Ok) {
      alert('success');
    }
    else {
      alert('problem');
    }
},

If you need I can also explain how to do it by returning a error 500, and get the error in the event error (ajax). But in your case this may be an option

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